STUTTGART, Germany — The U.S.-led NATO alliance will launch its largest war games since the end of the Cold War on Thursday, pulling together 50,000 troops, 65 warships and 250 planes for a mission that will test the ability of allies to free a member state.

“The exercise will test our readiness to restore the sovereignty of an ally — in this case, Norway — after an act of armed aggression,” NATO Secretary-General Jens Stoltenberg said Wednesday ahead of the launch of this year’s Trident Juncture exercise.

The drills amount to launching a liberation campaign — a worst-case scenario for NATO. Stoltenberg said the exercise is against a “fictitious aggressor.” But Trident Juncture was designed to simulate a “near-peer” adversary, and the only one in the neighborhood is Russia.

Since 2014, NATO and U.S. forces in Europe have steadily increased the size and complexity of military drills as the alliance adapts to what they’ve deemed a “new security environment” on the Continent.

For NATO, Russia’s intervention and annexation of territory in Ukraine more than four years ago triggered an overhaul in how allies operate in Europe. Since then, every year has marked expanded drills, troops rotations into central and Eastern Europe, and frequent declarations about the U.S. and allies involved in some form of post-Cold War first.

In the case of Trident Juncture, the USS Harry S. Truman Carrier Strike Group is joining the drills and sailing into the Arctic Circle, the first time for a U.S. carrier there since 1987.

Trident Juncture participants will split into “south” and “north” forces, taking turns in the role of aggressor against NATO defending forces.

The drills also will test the ability of allies to reinforce an allied country with troops and equipment from the U.S. and Europe, as well as certify the readiness of NATO quick-reaction forces.

For NATO, the logistics of moving forces in a crisis across the Atlantic and around Europe — with speed and security — has long been a source of concern. Earlier this year, allies agreed to stand up two new headquarters that harken back to NATO’s Cold War-era command structure in hopes of addressing those concerns.

“So Trident Juncture sends a clear message to our nations and to any potential adversary,” Stoltenberg said. “NATO does not seek confrontation. But we stand ready to defend all allies.”

Moscow, meanwhile, has complained about the exercise, which it regards as a provocation. Such criticisms are nothing new. Nearly every NATO troop rotation in Eastern Europe or war game in a state that borders Russia is met with criticism from Russian officials.

At the same time, Russia also has carried out large war games near NATO territory in recent years and built up forces in border areas like the military enclave of Kaliningrad, which borders Poland and Lithuania.

Unlike Russia, NATO is “transparent in the way we exercise,” Stoltenberg said.

Russia was briefed on the exercise and accepted an invitation for its representatives to attend Trident Juncture as an observer. Yet Russia has not notified NATO of “a single exercise since the end of the Cold War,” Stoltenberg said. Stoltenberg did not consider Russia’s invitation to its Zapad exercise last year proper because it did not meet international protocols.

Trident Juncture is being led by U.S. Navy Adm. James Foggo, head of NATO’s Allied Joint Force Command-Naples, who will command aboard the USS Mount Whitney.

Maritime operations play a large role in the exercise.

“The Atlantic is vital for the security of Europe and for global trade and communications,” Stoltenberg said. “It also provides a crucial route for reinforcement between North America and Europe. NATO is committed to securing the Atlantic.”

All 29 NATO members are taking part in the war games. The U.S. is the largest participant with more than 14,000 servicemembers drawn from the Army, Air Force, Navy and Marine Corps.